Australian Wood Review – June 2019

http://www.woodreview.com.au 37

TOOLS & EQUIPMENT

1. Veritas Tools (Canada) now manufacture
   chisels and plane blades in PM-V11
   steel. Their own test results determined
   this alloy will provide a balance of edge
   retention, impact resistance and ease of
   sharpening. Photo: Lee Valley, Canada


2. Good quality high carbon steel chisels
   like these from Titan are good value
   and perform very well. Avoid the upper
   example (firmer chisel) as you may
   have difficulty fitting them into a side-
   clamping type of honing guide.


3. There are many examples of high quality
   Japanese chisels of the water quenched
   high carbon steel type. If you use
   a honing guide be aware that some
   examples are either too short to fit
   into a honing guide or have a triangular
   section which also does not fit.
   Photos this page: Peter Young

T

here is now a confusing array of
steels available for both chisels
and plane blades and choosing the
right steel for your purpose can be
daunting. I am not a metallurgist
but I do have some experience with
various types of steel in different
applications, so what follows is my
personal take on this issue. Other
experienced people may have different
views so it’s always good to get a
number of opinions. A good source
of information about steel types and
sharpening techniques is Ron Hock’s
book The Perfect Edge published by
Popular Woodworking Books.

The important take-home message
is that choosing a suitable chisel or
plane blade is a compromise and
there are a number of factors which
need to be taken into consideration.
Different people will place a different
emphasis on each of these factors.

In many magazine reviews there
is a very heavy emphasis on edge
retention because logically the better
the edge retention the longer the
period between sharpening. However

it’s also true that the better the edge

retention, the more expensive the

item is going to be. All cutting tools

need to be frequently sharpened

to perform at their best, it’s just a

question of how often you sharpen

and how long that takes.

Steel types

Steel is essentially an alloy of iron and

carbon. The addition of only very small

amounts of carbon (as little as 0.2%)

turns iron into an incredibly strong

but malleable material and most of

the steel we come across is in this low

carbon form. Adding more carbon

increases hardness (resistance to

compressive deformation) and tensile

strength (resistance to elongation).

With about 0.8% carbon, steel is

easily able to be hardened with

heat treatment. With improved

hardness comes improved resistance

to abrasion or for the woodworker,

improved ability to hold a cutting

edge. However if too much carbon

is added (more than 1.5%) the steel

becomes brittle with fracturing of

the cutting edge.

There are three important steps

in steel manufacture. Firstly the

ingredients must be heated for the

alloy to form. Secondly, the steel must

be cooled (quenched) but in such a

way as to retain hardness. Thirdly, the

hard (but brittle) steel needs to be

tempered to reduce brittleness.

Tempering must be done in a very

controlled manner as uncontrolled

tempering can reduce hardness and

thus edge life. A good example of

uncontrolled tempering (heating)

is when blades are being ground on

a grinding wheel. It is very easy to

overheat the thin cutting edge and

thus lose hardness exactly where

you want it. Cooling the blade

in water when grinding is also a

common practice but this should be

discouraged for all except high carbon

steel. A2 steel is especially prone to

losing hardness with uncontrolled

heating and you should only use a

heat sink, for example, a metal block

for cooling.

Tool steels are described according to

the method used for quenching.

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